You can get a 3.2Tb SSD if you have 15 grand spare. But you can get 1Tb HDD for £40 ish so I wouldn't bother yet. Use SSD for the OS and frequently accessed files, and HDD for bulk storage.
As for HDD in the laptop, well I didn't want to pay very much for a work computer, that's the simple answer. You get what you pay for I guess but it still cost me more than I'd pay for a quiet desktop machine. I didn't expect that level of rubbish, at any rate.